Surface finishing impregnated fabrics



June 25, 1946. H. SNOW ETAL SURFACE FINISHING IMPREGNATED FABRICS 2Sheets-Sheet 1 Filed April 12, 1944 Snucntors:

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June 25, 1946. I H, sN w AL 2,402,689

- SURFACE FINISHING EM Filed April 12, 1944 2 Sheets-Sheet 2 PatentedJune25, 1946 SURFACE FINISHING IMPREGNATED FABRICS Howard Snow and SaraD. lickard, Charlotte, N. C., assignors to Southern Friction MaterialsCompany, a corporation of North Carolina Application April 12, 1944,Serial No. 530,648

5 Claims. (01. 51-281) Our invention relates to impregnated fabrics andmore particularly to a method for surface treating such fabrics toremove incrustations of the impregnating material and to obtain .thedesired physical characteristics of such fabrics.

When fabrics are impregnated with resinous thermosetting materials andsubsequently heat treated or cured, as it is known in the art, theimpregnating material thicken and harden and have a tendency to form astiff, hard crust on the surface of the treated fabric. Heretofore thesurfaces of such fabrics have been ground with an emery wheel or wirebrush to produce a leveling of the surface and to provide flexibility.These operations are subject to the disadvantage of some disintegrationof the fabric or fibrous material, resulting in weakening of thestrength of the finished product. Also, the excess friction that isgenerated in these operations frequently produces burning or blisteringof the fibers, which likewise results in loss of strength.

In accordance with our invention, we have developed a procedure .bywhich the desired surface characteristics of the impregnated fabric canbe obtained without any substantial deterioration of the product and atthe same time overcome the usual stiffness of the impregnated productcaused by the hardened or cured resinous constituents. The result ofthis procedure is a unifQrmIysmooth surface, on a flexible product whichhas relatively 30 great strength and water resistance and whichpossesses sumcient flexibility to make the product useful as asubstitute for leather in many instances.

The characterizing features of our new process comprise a preliminaryheating and partial softening of the impregnated fabric in hot water orsteam, which also wets the surface of the fabric to some extent; and thesubsequent abrading of this softened wet product by bringing it intomoving contact with rotating rolls having an abrading material orsurface. The preliminary heat treatment conditions the impregnatedfabric so that it may be abraded more easily and prevents the scorchingor burning of high spots on the fabric. Furthermore, the softening andwetting eflects of the preliminary treatment produce somewhat of a flowof the surface materials during the abrading operation, so that thefinal product has a smooth, uniformly abraded surface. This operationeffects removal of the crust of impregnating materials and therebyimparts flexibility to the otherwise stiff product.

As an illustrative but non-limiting example of 2 ical commercialoperation which has been practiced on a substantial scale, is given:

A cotton fabric of the nature of cotton belting or "drier felt materialis impregnated with a resinous chemical composition, such as forexample, the composition disclosed in a co-pending application SerialNo. 490,877, filed June 15, 1943. The impregnated fabric is "cured byheating to a temperature of about 250 F. for a period of about 24 to 48hours, after which it is then ready for surface treatment. Theimpregnated and cured fabric is placed in a heated water bath, forexample, a barrel containing water continuously heated by introductionof live steam. The product is permitted to remain in the hot water for aperiod of a minute or more to effect softening and wetting of thematerial as described above. It is then placed upon a movable support orcarriage and passed through a sanding machine having a plurality ofrolls covered with sand paper. The fabric is brought into contact withthe surface of these rotating rolls and the crust or surface impregnanton the fabric is quickly removed and without generation of any heatsufhcient to damage the fabric.

The term "sand paper" as used herein is intended to apply to those typesof sand paper or emery cloth or the like that are adapted for wetsanding or abrading operations generally, and. particularly for theimpregnated fabric of this invention. Illustrative examples of such sandpaper, which. we have used successfully in commercial operations, arewaterproof "Silicon Carbide Cloth #24-X, and Speed-Wet Durite Cloth#2441 manufactured .by the Behr-Manning Company, Troy, New York. Thesesandpapers have somewhat medium size grit particles which areparticularly suited for .wet sanding of the product of this invention.If the grit is too coarse, it will mark the fabric and if it is toofine, it will not remove the abraded dust efilciently.

The fabric may be abraded only on one side as described above; or ifdesired, it may be turned over and passed again through the abradingmachine, so as to give the other side of the fabric similar treatment.After this operation, the impregnated fabric is ready for drying,packaging and shipment.

Instead of the above batch type of operation, the method of ourinvention may be carried out in a continuous manner from a continuousroll of the fabric or web material which would be passed slowly througha heated water bath and the method of our invention, the following typ-56 then through the sanding machine and after- 3 wards wound orotherwise packaged for use and shipment.

The hot water treatment referred to above may be augmented or modifiedby the use of chemicals where special surface effects on the materialare desired. For example, if a somewhat softer or smoother or slickerfinish is required for the abraded material, we have found that markedlyimproved results along these lines may be obtained by use of waxyemulsions in the treating bath. Special surface effects may also beproduced by the use of water soluble phenol formaldehyde resins, and bydrying oil or varnish emulsions. A non-limiting but illustrativeexample, is the use of a water emulsion containing a water dispersiblewax in combination with an aluminum acetate water repellent materialsuch as the product commercially known as Paratex, sold by the CharlotteChemical Laboratories, Inc., Charlotte, N. C. These emulsions orsolutions facilitate the grinding operation as well as conditioning thesurface of'the fabric, so that an extremely smooth and uniformly groundsurface is finally obtained. When it is desired to color the fabricsuitable dyes may be incorporated in the above water emulsion.

The method of our invention may be carried out with varying types ofequipment, and in the accompanying drawings we have illustrateddiagrammatically two respective examples of batch and continuoussystems.

Figure 1 is a diagrammatic illustration of the batch system; and

Figure 2 is a diagrammatic illustration of the continuous system.

In the batch system shown in Fig. 1 of the drawings, the stack or othersupply of impregnated and cured fabric sheets are illustrated at In andthe flow of the procedure or method is shown in the succeeding parts ofthis figure. These comprise a treating bath ll, which may contain onlywater or may comprise one or more of. the waxy, resinous or oilemulsions mentioned above. Suitable means for heating this bath to atemperature of about 175 F. are supplied. This may be in the form oflive steam introduced through a steam pipe shown at 12.

After the fabric sheet has been conditioned in the treating bath I I, itis placed upon a supporting member which serves to hold it in proper,unwrinkled position while it is being abraded. This supporting membercomprises a wooden board 13 which has a rubber mat covering I4 forholding the conditioned fabric sheet l5. This rubber mat functions in amost practical and efficient manner to hold the fabric sheet in placeand in a fiat, smoothcondition while it is being passed in contact withthe series of abrading rolls shown at l6. These rolls maybe of metal orother suitable material and have a sand paper covering indicatedat ll.The moisture and/or chemical emulsion previously applied to the treatedfabric sheet serves to-wet the sand paper and effect the desiredlow-temperature abrading, to provide a smooth, unscorched surface on thefinally treated sheets which are shown at l8.

The continuous method diagrammatically illustrated in Fig. 2 shows asupply roll [9 of the treated fabric in continuous web form. Thetreating bath is indicated at 20 and the web material is guidedtherethrough by means of guide rolls 2|. Following the treating bath,the.web is passed underan'd in contact with the rotating rolls l6,

4 and is held in movable, frictional contact therewith by a suitablesupport 22. The finished material is guided around roll 23' and woundupon finishing roll 24.

Various other modifications and changes may be made in the foregoingprocedure, materials and conditions without departing from the scope ofour invention some of the novel features of which are ,defined in theappended claims.

We claim:

1. A method of abrading without deleteriously affecting impregnatedfabric material treated with an impregnant which tends to thicken andharden upon curing to form a stiff, hard crust on the surface of theimpregnated material, but which is slightly heat-softenable so that theim-: pregnated material may be rendered limp by heating, comprisingheating and wetting the impregnated material sufficiently to causeincipient softening of the impregnant and wetting of the surface of thematerial, and then bringing the thus treated material into abradingcontact with rotating rolls having abrading surfaces so as to remove thecrust of the impregnant from the material and provide a uniformlyabraded surface thereon.

2. A method of abrading a resinous impregnated fabric treated with aresinous impregnant which tends to thicken and harden upon curing toform a stiff, hard crust on the surface of the impregnated fabric, butwhich is slightly heatsoftenable so that the impregnated fabric may berendered limp by heating, said abrading being carried out to remove thesurface incrustating materials and impart flexibility to the fabricwithout damaging the strength thereof, comprising heating the fabric toeffect slight softening of the impregnating material on the surface ofthe fabric, wetting said surface and passing the thus treated materialover an abrading surface.

3. A method of abrading a resinous impregnated fabric toremove thesurface incrustating materials and impart flexibility to the fabricwithout damaging the strength thereof, comprising immersing theimpregnated fabric in hot water for a short length of time to effectpartial softening and surface wetting of the impregnated material, andthen bringing the wet fabric into moving contact with rotating abradingrolls.

4. A method of abrading a resinous impregnated fabric to remove thesurface incrustating materials and impart flexibility to the fabricwithout damaging the strength thereof, comprising immersing theimpregnated fabric in an emulsion adapted to wet the surface of thematerial and to facilitate surface grinding, and bringing the thustreated fabric into moving contact with rotating abrading rolls.

5. A method of'abrading a resinous impregnated fabric to remove thesurface incrustating materials and impart flexibility to the fabricwithout damaging the strength thereof, comprising immersing theimpregnated fabric in a heated aqueous waxy emulsion to wet andcondition the surface of the fabric for abrading, and abrading the thustreated fabric surface by bringing it into moving, frictional contactwith sand paper, so as to remove the surface crust of the impregnatingmaterial from the fabric and provide a smooth, slick finish thereon.

HOWARD SNOW. SARA D. PICKARD.

